At the present time, an organic electroluminescent element is attracting attention as a thin light-emitting material.
An organic light-emitting element makes use of electroluminescence (EL) of an organic material (hereafter, it is also called as “an organic EL element”). It is a fully solid element which is capable of emitting light with a low voltage such as about several V to several ten V. It has many excellent features of high luminance, high light-emission efficiency, thin and small weight. Accordingly, it has been attracted attention in recent years used for: various display backlights; a display board such as signboard and emergency lamp; and a surface light-emitting body for illumination source.
The organic EL element has a structure in which a light-emitting layer containing an organic material is located between a pair of electrodes, and emitted light in the light-emitting layer is extracted to the outside through the electrode. Therefore, at least one of the pair of electrode is composed of a transparent electrode, and the emitted light is taken out from the transparent electrode side. Moreover, the organic EL element can produce high luminance at a low electric power, and it is excellent in the points of visibility, response speed, lifetime and electric power consumption.
To this organic EL element, it is provided a production method of an organic EL element having a light-emitting pattern. In this method, a non-light-emitting portion is formed in an organic functional layer laminated on a glass substrate by irradiating with UV rays to result in deteriorating the irradiated portion (for example, refer to Patent Document 1 and Patent Document 2).
Further, it is possible to form a light-emitting pattern having a light-emitting luminance of multiple tones if an amount of irradiation is changed when a patterning is done by irradiating the organic EL element with UV rays.
However, when a natural image whose light-emitting luminance is continuously changed is subjected to patterning, it often results in producing an image having different gradation properties from the original image. When a natural image having a continuous gradation is patterned, the produced image becomes unnatural, and it has been difficult to obtain a required image.